Water absorbent composition

ABSTRACT

A composition comprising at least one superabsorbent polymer and at least one water soluble phosphate and optionally a plant advantageous additive.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a composition having improved waterabsorbency.

BACKGROUND AND PRIOR ART

Superabsorbent polymers absorb water or fluids several times theirweight. Superabsorbent polymers or SAPs improve supply of water in thesoil and therefore find use in agriculture.

Various superabsorbent polymers are known in the art. Suchsuperabsorbent polymers may be made from polyacrylamide copolymer,cross-linked carboxymethylcellulose, polyvinyl alcohol copolymers,cross-linked polyethylene oxide, starch grafted copolymer ofpolyacrylonitrile etc. The water absorbance of most superabsorbentpolymers has been known to decrease considerably in the presence ofsalts. Soil incorporated superabsorbent polymers or those that are mixedwith fertilizers have been known to suffer from decreased absorbancecapacity due to the presence of salts in the soil or fertilizer. Studieshave been carried out to study the effect of such salts such as thosecarried out by Daniel C. Bowman, Richard Y. Evans, and J. L. Paul., J.Amer. Soc. Hort. Sci. May 1990 115:382-386, Fertilizer Salts ReduceHydration of Polyacrylamide Gels and Affect Physical Properties ofGel-amended Container Media. The paper discusses the decrease in polymerabsorption capacity when mixed with salts. They observed that solublesalts dramatically affect absorption by hydrophilic polyacrylamide gels.

Agriculture requires the use of many compounds to ensure good yields andhealthy crops. Most of the fertilizers and nutrients added to the soilare salts that in some way contribute to the improvement in the crops.Salts are also naturally present in the soil, which also contribute tothe increased salinity of the soil. In draught prone areas and areaswhere water management is essential, the salinity in the soil is higher,as water required to wash these salts away is scarce. In such soils,where water is scarce or where water management is required or evenwhere normal salts are added to the soil, addition of superabsorbentpolymers may not result in the desired effect that is, increased wateravailability. Salts in the environment around the superabsorbent polymerdecrease the capacity of the polymer to absorb and desorb water.

Specifically when mixed with soil for agricultural purposes,superabsorbent polymers are expected to perform exceptionally well byabsorbing water many times the weight of the polymer. When introducingother components such as fertilizers etc., the capacity of thesuperabsorbent polymers to absorb water decrease considerably, naturallypresent salts in the soil may also contribute to a decrease inabsorption capacity.

EP1740232B1 (Qin et. al) teaches the use of a combination of twomaterials which are then surface coated onto the superabsorbent polymer.The materials include thermoplastic materials such as polyethyleneoxide, polypropylene oxide, hydroxypropyl cellulose, polyethylene imine,polyvinyl alcohol, polyethylene glycol, polyacrylate, polystyrene,polyamide etc. Applications of such material may be useful forsuperabsorbent polymers used in sanitary and industrial uses, but inagricultural uses, many of the additives used may not be useful, and mayeven hinder the flow of water from the superabsorbent polymer back intothe soil.

WO2008025656 (Herfert et. al) teaches the use of polyamines to surfacetreat superabsorbent polymers to improve absorption. The use ofpolyamines is expensive and the process requires heating and cooling ofthe polymer gel.

WO2002060983 (Thomas et. al) teaches the use of water insoluble metalphosphates to improve absorption of superabsorbent polymers whenintroduced into an environment which is saline. The water insolublephosphate confers high absorption capacity, improved liquid transportperformance and faster swelling speed to the superabsorbent polymer.However, it has been observed by the present inventors that theinsoluble nature of the phosphates taught in Thomas is also responsiblefor partially restricting the water absorptive capacity of theassociated polymer. This publication also teaches the use of an waterinsoluble phosphate, along with a superabsorbent polymer, only in apersonal care and hygiene environment of use.

Many other efforts have been made in the past to improve absorbance ofsuperabsorbent polymers in the presence of salts. Most of these effortshave been directed to improving the water absorbance of superabsorbentpolymers only in the personal hygiene products.

OBJECT OF THE INVENTION

Thus, one advantage of the present invention is in providing acomposition having enhanced water absorption capacity.

Another advantage of the present invention is in providing a compositionhaving enhanced water absorption capacity even in the presence of anionic salt.

Yet another advantage of the present invention is in providing acomposition having enhanced water absorption capacity wherein thecomposition is suitable for agricultural use.

Another advantage of the present invention is in providing a compositionhaving enhanced water absorption capacity and capable of performing as asynergist to a pesticide during its agricultural use.

These and other advantages may be achieved by the invention described inany aspect or embodiment hereinafter.

SUMMARY OF THE INVENTION

A composition comprising at least one superabsorbent polymer and atleast one water soluble phosphate.

A method of increasing the water absorption capacity of a superabsorbentpolymer, the method comprising contacting the superabsorbent polymerwith at least one water soluble phosphate.

A composition comprising at least one superabsorbent polymer, at leastone water soluble phosphate and at least one plant advantageousadditive.

A multi-pack agricultural product comprising:

a first container comprising at least one superabsorbent polymer;

a second container comprising at least one water soluble phosphate; and

an instruction manual instructing an user to admix the contents of saidfirst and second container and administering the admixture to a locus.

DETAILED DESCRIPTION

It has surprisingly been found by the present inventor that, contactinga superabsorbent polymer with at least one water soluble phosphatedemonstrates an increased absorbance of water, even under conditions inthe soil that normally contribute to decrease in water absorbance ofsuch superabsorbent polymers. It was further surprisingly found thatthis enhancement in the water absorption capacity induced due to a watersoluble phosphate was unexpectedly higher than the enhancement observeddue to a water insoluble phosphate, for example, taught in Thomas et aldiscussed above.

Without wishing to be bound by theory, it is believed that contacting asoluble phosphate with a superabsorbent polymer matrix causes thesolubilized (dissolved) phosphate to ionize. The resulting ions migratemore readily into the superabsorbent polymeric core and settle into thecarboxylic acid—amide network, which is responsible for waterabsorption. This migration of the dissolved phosphate ions into thepolymeric core increases the total number of ionic moieties present inthe polymeric core, consequently increasing the number of availablesites for hydrogen bonding with water molecules, as well as altering thepore size of the polymeric network. The present inventors also believethat the use of a water soluble phosphate provides the followingunexpected advantages: alter the total tertiary structure of the polymerto accommodate more water molecules, alter the acid to amide ratio,cause the surface crosslinking of the polymer to bind more watermolecules, water soluble phosphate acts as a potential fertilizersource, and act as a potential synergist for enhancing the knownefficacy of the pesticides. Naturally, these unexpected benefits couldnot have been conceivably achieved with a water insoluble phosphate.

Accordingly, in an aspect, the present invention provides a compositioncomprising at least one superabsorbent polymer and at least one watersoluble phosphate.

Alternately, in another aspect, the present invention also provides amethod of increasing the water absorption capacity of a superabsorbentpolymer, the method comprising contacting the superabsorbent polymerwith at least one water soluble phosphate.

Within the context of this specification, each term or phrase below willinclude the following meaning or meanings:

The terms “superabsorbent polymer” or “SAP” or “polymer gel” refer towater swellable polymers that can absorb water many times their weightin an aqueous solution. Without wishing to be bound by theory, the termsuperabsorbent polymers also apply to polymers that absorb water as wellas de-sorb the absorbed water. The superabsorbent polymer may beselected from but not limited to water-swellable or water absorbing orwater-retentive polymers such as cross-linked polymers that swellwithout dissolving in the presence of water, and may, absorb at least10, 100, 1000, or more times their weight in water.

The term contacting the water soluble phosphate with the superabsorbentpolymer includes, but is not limited to, the application of the watersoluble phosphate onto or in the vicinity of the surface of a particleof a superabsorbent polymer.

“Water soluble phosphates” refers to those salts of phosphate that arewater soluble or at least slightly soluble in water under conditions ofnormal temperature and pressure.

In an embodiment, the term water soluble phosphate, includes a phosphatesalt, having a solubility greater than about 1 g in 100 mL of water at25° C.

The phrases “at least one” means “one or more”, “at least” followed by anumerical value means “this or a higher numerical value”.

Thus, in an aspect, the present invention also provides a superabsorbentpolymer whose particles are contacted with a water soluble phosphate.These particles of the superabsorbent polymer possess significantlyenhanced water absorption capacity, and were found especially suited foragricultural uses.

In an embodiment, the water soluble phosphates may be water solublealkali phosphates and may be of the general formula:

M_(a)H_(b)P_(c)O_(d) where a may be 1-15, b may be 0-14, c may be 1-5and d may be 1-15;

wherein M may be an alkali metal ion or NH₄ ⁺.

In a preferred embodiment, the water soluble phosphate may be selectedas comprising such exemplary alkali metal ions selected from Li⁺, Na⁺,K⁺, Rb⁺, Cs⁺, Fr⁺, H⁺ and NH₄ ⁺.

In yet another embodiment, the preferred water soluble phosphate may beselected from Na⁺, K⁺, NH₄ ⁺ salts of phosphate.

In another embodiment, the preferred water soluble phosphate may beselected from water soluble-mono, di-, tri-, tetra-, and polyphosphatesalts of alkali metal ions that are water soluble.

In another embodiment, the water soluble phosphate may be selected frommonosodium dihydrogen phosphate, disodium hydrogen phosphate, trisodiumphosphate, diammonium phosphate, monoammonium phosphate, monopotassiumphosphate, potassium diphosphate and dipotassium phosphate.

In an embodiment, the amount of water soluble phosphate may be at least0.1% based on the weight of the superabsorbent polymer. Preferably theamount of water soluble phosphate may be at least 0.1% to 50% based onthe weight of the superabsorbent polymer. Preferably the amount of thewater soluble phosphate may be at least 0.1-25% based on the weight ofthe superabsorbent polymer. Most preferably the amount of the watersoluble phosphate may be at least 0.1-10% based on weight of thesuperabsorbent polymer.

In an embodiment, the superabsorbent polymer may be a selected from, butnot limited to, copolymer of acrylamide and sodium acrylate; hydrolyzedstarch-polyacrylonitrile; 2-propenenitrile homopolymer, hydrolyzed,sodium salt or poly(acrylamide co-sodium acrylate) orpoly(2-propenamide-co-2-propanoic acid, sodium salt);starch-g-poly(2propenamide-co-2-propanoic acid, mixed sodium andaluminum salts); starch-g-poly(2-propenamide-co-2-propanoic acid,potassium salt); poly(2-propenamide-co-2-propanoic acid, sodium salt);poly-2-propanoic acid, sodium salt; starch-gpoly(acrylonitrile) orpoly(2-propenamide-co-sodium acrylate); starch/acrylonitrile copolymer;crosslinked copolymers of acrylamide and sodium acrylate;acrylamide/sodium polyacrylate crosslinked polymers; anionicpolyacrylamide; starch grafted sodium polyacrylates; acrylic acidpolymers, sodium salt; crosslinked potassium polyacrylate/polyacrylamidecopolymers; sodium polyacrylate; superabsorbent polymer laminates andcomposites; partial sodium salt of crosslinked polypropenoic acid;potassium polyacrylate, lightly crosslinked; sodium polyacrylate,lightly crosslinked; sodium polyacrylates; poly(sodiumacrylate)homopolymer; polyacrylamide polymers, carrageenan, agar, alginic acid,guar gums and its derivatives, and gellan gum; Specific superabsorbentpolymers include crosslinked copolymer of acrylamide and potassiumacrylate.

In a preferred embodiment, the superabsorbent polymer may bestarch-g-poly (2-propenamide-co-2-propenoic acid) potassium salt orcrosslinked polyacrylic acid potassium salt.

Thus, in an embodiment, the present invention provides a compositioncomprising at least one superabsorbent polymer and at least one watersoluble alkali phosphate having the general formula M_(a)H_(b)P_(c)O_(d)where a can be 1-15, b can be 0-14, c can be 1-5 and d can be 1-12 andwherein M may be an alkali metal ion or an NH⁴⁺.

In another embodiment, the present invention provides a compositioncomprising starch-g-poly (2-propenamide-co-2-propenoic acid) potassiumsalt polymer and at least one water soluble alkali phosphate having thegeneral formula M_(a)H_(b)P_(c)O_(d) where a can be 1-15, b can be 0-14,c can be 1-5 and d can be 1-12 and wherein M may be an alkali metal ionor an NH⁴⁺.

In another embodiment, the present invention provides a compositioncomprising starch-g-poly (2-propenamide-co-2-propenoic acid) potassiumsalt polymer and at least one water soluble alkali phosphate having thegeneral formula M_(a)H_(b)P_(c)O_(d) where a can be 1-15, b can be 0-14,c can be 1-5 and d can be 1-12 and wherein M may be an alkali metal ionor an NH⁴⁺.

In a particular embodiment, the present invention provides a compositioncomprising starch-g-poly (2-propenamide-co-2-propenoic acid) potassiumsalt polymer and trisodium phosphate.

It has been further found by the present inventors that the watersoluble phosphate of the present invention is simultaneously also apotential synergist for enhancing the known efficacy of the pesticideswhen the two are used in combination.

Therefore, in this aspect, the present invention provides a compositioncomprising at least one superabsorbent polymer, at least one watersoluble phosphate and at least one plant advantageous additive.

In an embodiment, the plant advantageous additive is selected fromfertilizers, mycorrhiza, micronutrients, acaricides, algicides,antifeedants, avicides, bactericides, bird repellents, chemosterilants,fungicides, herbicide safeners, herbicides, insect attractants, insectrepellents, insecticides, mammal repellents, mating disruptors,molluscicides, nematicides, plant activators, plant-growth regulators,rodenticides, synergists, virucides, derivatives thereof, biologicalcontrol agents and mixtures thereof.

In an embodiment, the fertilizer may be selected from organic andinorganic fertilizers such as those selected from but not limited tourea, NPK, nitrogen based fertilizers, phosphate, calcium, potassium,magnesium, sulfur, copper, iron, manganese, molybdenum, zinc, nickel,cobalt, boron and their salts and derivatives. Exemplary organicfertilizer may be selected from peat, limestone, rock phosphate, bloodmeal, bone meal, compost, humic acid, seaweed extracts, digestedproteins, fish meal, feather meal, corn meal, alfalfa meal etc.

In a preferred embodiment, the fertilizer may be an inorganic fertilizerselected from NPK, derivatives of potassium, zinc, phosphate such asthose selected from but not limited to potassium fertilizers such aspotassium carbonate, potassium chloride (also known as muriate ofpotash), potassium sulfate, potassium nitrate, sulfate of potashmagnesia; zinc fertilizers such as those selected from zinc sulfate,zinc oxide, zinc ammonia complex; phosphate fertilizer such asDi-ammonium phosphate, Monoammonium phosphate, Ammonium polyphosphate,Triple superphosphate or mixtures thereof.

In an embodiment, the fertilizer may be an organic fertilizer selectedfrom urea, rock potash seaweed extract, compost, humic acid, alfalfameal, corn meal, and mixtures thereof.

In an embodiment, the present invention may provide a compositioncomprising at least one superabsorbent polymer, at least one watersoluble phosphate and a fertilizer mix of organic and inorganicfertilizers.

In any aspect or embodiment described hereinafter, the term“composition” shall be intended to include both the compositions formedat the time of, or immediately before, the intended application or apre-formulated composition.

In an aspect, the composition may additionally comprise mycorrhiza,micronutrients including but not limited to amino acids and otheragronomically advantageous plant additives thereof.

Further additives such as inert fillers, binding agents, surfactants,dispersing agents and the like may be added to the composition of thepresent invention.

In an embodiment, the inert fillers and/or binding agents may beselected from but not limited to kaolin, sucrose, lactose, mineralearths and clays such as bentonite, perlite, talc, kaolin, aluminumsilicate, diatomaceous earth, attapulgite, clay, barium sulfate, mica,zeolites, calcium carbonate, fused sodium potassium, precipitatedsilica, precipitated silicates, aluminum silicate, sodium citrate,potassium citrate and magnesium citrate.

The improved composition of the present invention may be applied ingranular form, or in a powder form or in a liquid form or in any otheragrochemically acceptable form of delivery.

In a preferred embodiment, the improved composition of the presentinvention is in the form of granules.

The composition of the present invention may be applied to plant, root,seed, or seedling by various methods, including, but not limited todipping the plant, root, seed, or seedling into the superabsorbentpolymer composition, a slurry of the superabsorbent polymer composition,or a paste including the superabsorbent polymer composition of theinvention; mixing another plant growth media with the superabsorbentpolymer composition and later planting a plant, root, seed, or seedlinginto the plant growth media comprising the superabsorbent polymercomposition of the invention; or forming a slurry of the superabsorbentpolymer composition that is applied directly to the growing substrate.

In another aspect, the present invention provides a process for thepreparation of a composition. The process comprises mixing asuperabsorbent polymer and a water soluble phosphate.

The word “mixing” is to be taken in the broadest possible sense whereinit may imply that the superabsorbent polymer may be added to the watersoluble phosphate, or to a solution of the water soluble phosphate or bycontacting a salt forming solution such that a water soluble phosphatemay be formed when contacted within the superabsorbent polymer.

In an embodiment, the superabsorbent polymer may be selected from butnot limited to copolymer of acrylamide and sodium acrylate; hydrolyzedstarch-polyacrylonitrile; 2-propenenitrile homopolymer; hydrolyzedsodium salt of poly(acrylamide co-sodium acrylate) orpoly(2-propenamide-co-2-propanoic acid, sodium salt);starch-g-poly(2propenamide-co-2-propanoic acid, mixed sodium andaluminum salts); starch-g-poly(2-propenamide-co-2-propanoic acid,potassium salt); poly(2-propenamide-co-2-propanoic acid, sodium salt);poly-2-propanoic acid, sodium salt; starch-g-poly(acrylonitrile) orpoly(2-propenamide-co-sodium acrylate); starch/acrylonitrile copolymer;crosslinked copolymers of acrylamide and sodium acrylate;acrylamide/sodium polyacrylate crosslinked polymers; anionicpolyacrylamide; starch grafted sodium polyacrylates; acrylic acidpolymers, sodium salt; crosslinked potassium polyacrylate/polyacrylamidecopolymers; sodium polyacrylate; superabsorbent polymer laminates andcomposites; partial sodium salt of crosslinked polypropenoic acid;potassium polyacrylate, lightly crosslinked; sodium polyacrylate,lightly crosslinked; sodium polyacrylates; poly(sodiumacrylate)homopolymer; polyacrylamide polymers, carrageenan, agar, alginic acid,guar gums and its derivatives, gellan gum and crosslinked copolymer ofacrylamide & potassium acrylate.

In a preferred embodiment, the superabsorbent polymer may bestarch-g-poly (2-propenamide-co-2-propenoic acid) potassium salt orcrosslinked polyacrylic acid potassium salt.

In an embodiment, the amount water soluble phosphate may be at least0.1% of the total weight of the superabsorbent polymer. Preferably theamount of water soluble phosphate may be at least 0.1% to 20% of thetotal weight of the superabsorbent polymer. More preferably the amountof water soluble phosphate may be at least 0.1% to 10% of the totalweight of the superabsorbent polymer.

In another embodiment, the present invention provides a process forpreparing a granular composition, said process comprising:

-   -   a. admixing an organic fertilizer or an inorganic fertilizer        with at least a binding agent;    -   b. adding a superabsorbent polymer and homogenizing the mixture;    -   c. adding at least one water soluble phosphate to the mixture;    -   d. adding water to the mixture of step (c) to form a dough;    -   e. granulating the dough; and    -   f. drying the granules of step (e).

In an embodiment, the granules may be formed by process of extrusion, orpan granulation, or fluid-bed granulation.

In an embodiment, the superabsorbent polymer may be present within thecompositions of the invention in the range of at least 0.1 to up to 100grams per 100 g by weight of the composition. In a preferred embodiment,the quantity of superabsorbent polymer may be in the range of at least0.1 to 50 grams per 100 g by weight of the composition. In a preferredembodiment, the quantity of superabsorbent polymer may be in the rangeof at least 0.1 to 10 gm per 100 g by weight of the composition.

In another aspect, the present invention provides a method of improvingthe quality of plants and/or soil comprising contacting the soil with acomposition comprising a superabsorbent polymer and a water solublephosphate.

In an embodiment, the method comprises applying the superabsorbentpolymer composition of the invention into the root zone of the plants.

In an embodiment, the present invention provides a method forimprovement of soil by application of the superabsorbent polymercomposition of the present invention.

In an embodiment, the present invention provides a method for improvingthe yield of a crop by applying the superabsorbent polymer compositionof the invention to plant propagation material selected from, but notlimited to seeds, plant propagules such as suckers, corms, bulbs, fruit,tubers, grains, cuttings and cut shoots.

In an embodiment, the present invention provides a method for improvingthe yield of a crop by applying the superabsorbent polymer compositionof the invention to roots of the plant.

In another embodiment, the present invention provides a method forimproving the yield of a crop by applying the superabsorbent polymercomposition of the invention to foliar parts of the plant.

In any aspect or embodiment described hereinabove, the term“superabsorbent polymer composition of the invention” shall beunderstood to include a composition comprising at least onesuperabsorbent polymer and at least one water soluble phosphate or acomposition comprising at least one superabsorbent polymer, at least onewater soluble phosphate and at least one plant advantageous additive.

In an aspect, the superabsorbent polymer, the water soluble phosphateand optionally the plant advantageous additive may be packaged as akit-of-parts which facilitates the addition of the superabsorbentpolymer, the water soluble phosphate and optionally the plantadvantageous additive at the time of application.

Therefore, in this aspect, the present invention provides a multi-packagricultural product comprising:

a first container comprising at least one superabsorbent polymer;

a second container comprising at least one water soluble phosphate;

optionally a third container comprising at least one plant advantageousadditive; and an instruction manual instructing an user to admix thecontents of said first and second container and administering theadmixture to a locus.

In another embodiment, the present invention can provide a multi-packproduct comprising:

-   (a) a first container comprising at least one superabsorbent    polymer; and-   (b) a second container comprising at least one water soluble    phosphate.

In this embodiment, the multi-pack superabsorbent polymer product canfurther comprise an instruction manual instructing the user to admix thecontents of said first and second containers and administering theadmixture to the locus.

In an embodiment, the multi-pack product may comprise a fertilizer orfertilizer blends or blends of fertilizer with other agronomicallyadvantageous plant additives.

In an embodiment, the present invention can provide a multi-packsuperabsorbent polymer product for application at a locus, said productcomprising:

-   (a) a first container comprising superabsorbent polymer or a    composition thereof;-   (b) a second container comprising at least one water soluble alkali    phosphate having the general formula M_(a)H_(b)P_(c)O_(d) where a    can be 1-15, b can be 0-14, c can be 1-5 and d can be 1-12 and    wherein M may be an alkali metal ion or an NH⁴⁺.

In this embodiment, the composition of superabsorbent polymer maycontain the superabsorbent polymer combined with fertilizers,micronutrients and other agronomically advantageous plant additives.

In an embodiment, the present invention can provide a single packproduct comprising, superabsorbent polymer and trisodium phosphate.

In an aspect, the present invention provides a method of using a watersoluble phosphate as a means to improve absorbance of a superabsorbentpolymer.

Thus, in an embodiment, the present invention provides a method ofenhancing the absorbance of a superabsorbent polymer, the methodcomprising contacting a water soluble phosphate with a superabsorbentpolymer, wherein the water soluble phosphate has the general formulaM_(a)H_(b)P_(c)O_(d) where a can be 1-15, b can be 0-14, c can be 1-5and d can be 1-12 and wherein M may be an alkali metal ion or an NH⁴⁺.

In a preferred embodiment, the water soluble phosphate may be thephosphate salt of ions selected from Li⁺, Na⁺, K⁺, Rb⁺, Cs⁺, Fr⁺, H⁺ andNH₄ ⁺.

In another embodiment, the water soluble phosphate may be selected fromNa⁺, K⁺ or NH₄ ⁺ salts of phosphate.

Preferred water soluble phosphate may be selected from watersoluble-mono, di-, tri-, tetra-, and polyphosphate salts of alkali metaland ammonium ions that are water soluble. The most preferred may beselected from monosodium phosphate, disodium phosphate, trisodiumphosphate, diammonium phosphate, monoammonium phosphate, monopotassiumphosphate, potassium diphosphate or dipotassium phosphate.

The advantages offered by the present invention will be more apparentfrom the examples set forth herein below. These examples are providedmerely as illustrations of the invention and are not intended to beconstrued as a limitation thereof.

EXAMPLES Example 1

Superabsorbent polymers were contacted with various substances that areconventionally known in the art to increase absorbance. These werecompared to superabsorbent polymers contacted with water solublephosphates. Table 1 compares the results:

TABLE 1 Wt. of water absorbed Water Wt. of by per gm absorbed polymer inof polymer Formulation in 24 hrs formulation in 24 hrs SAP plusfertilizer with tallow 17.652 0.386 56.17 amine surfactant SAP plusfertilizer with calcium 3.782 0.384 64.35 carbonate SAP plus fertilizerwith water 21.205 0.172 123.60 soluble phosphate SAP plus fertilizerwithout water 13.935 0.165 84.39 soluble phosphate SAP As such 64.9050.538 120.60

The superabsorbent polymer used for the experiment was the starch graftpolymer starch-g-poly (2-propenamide-co-2-propenoic acid) potassiumsalt. The water soluble phosphate used for the experiment was tri sodiumphosphate.

It was concluded that superabsorbent polymers when mixed with fertilizershowed markedly decreased absorbance. This decrease in water absorbancecould only be compensated by the addition of a water soluble phosphate.Compared to known methods of increased absorbance exemplified by calciumcarbonate and tallow amine surfactant, superabsorbent polymers treatedwith water soluble phosphates and mixed with fertilizers demonstratedimproved absorbance.

Example 2

Sr. Quantity No. Ingredient in Kg. 1 starch-g-poly(2-propenamide-co-2-propenoic acid) 32 potassium salt 2 PPT silica 19.23 Trisodium phosphate 4 4 Kaolin 44.8 Total 100

Process:

Precipitated silica and kaolin were mixed to which the superabsorbentpolymer trisodium phosphate was added. A required quantity of distilledwater was added while mixing to foam dough, this dough was extruded byusing extruder. The extruded granules were dried in Fluid bed drier. Thewater absorbance of the prepared composition was measured as shown inTable 1.

Example 3

Sr. No. Ingredient\Formulation Quantity 1 starch-g-poly(2-propenamide-co-2-propenoic acid) 6.4 potassium salt 2 Trisodiumphosphate 4 3 Kaolin 89.60 Total 100

Process:

The superabsorbent polymer, kaolin and trisodium phosphate were mixedwhile continuous blending. A quantity of distilled water was added whilemixing to form dough of the mixture. This dough was extruded by usingextruder. The extruded granules were dried in Fluid bed drier.

Example 4

Sr. No. Ingredient\Formulation Quantity 1 starch-g-poly(2-propenamide-co-2-propenoic acid) 72 potassium salt 2 Trisodiumphosphate 28 Total 100

Process:

The superabsorbent polymer was mixed with ground trisodium phosphate onpan granulator. A quantity of distilled water was sprayed slowly onmixture in pan granulator while mixing. The wet granules formed on pangranulator were dried in fluid bed dryer.

Example 5

Various water insoluble and water soluble phosphates were contacted withsuperabsorbent polymer and the absorbance in each case was studied.Table 2 compares the results:

Water absorption per gram of Water Soluble/ Superabsorbent Salt used informulation Insoluble Salt polymer. SAP + fertilizer without . . . 61.03water soluble phosphate. SAP + fertilizer + Tri Water Soluble 142.11sodium phosphate SAP + fertilizer + Water Soluble 129.73 Potassiumphosphate SAP + fertilizer + Sodium Water Soluble 118.52 di-hydrogenPhosphate SAP + fertilizer + Di- Water Soluble 124.23 ammonium PhosphateSAP + fertilizer + Zinc Water Insoluble 89.52 Phosphate SAP +fertilizer + Water Insoluble 74.40 Magnesium Phosphate SAP +fertilizer + Single Water Insoluble 80.33 super phosphate

The superabsorbent polymer used in the experiment was starch-g-poly(2-propenamide-co-2-propenoic acid) potassium salt.

It was concluded that superabsorbent polymers when mixed with waterinsoluble phosphates showed a marked decreased in absorbance, ascompared to water superabsorbent polymers that were mixed with watersoluble phosphates. Compared to known methods of increased absorbanceexemplified by water insoluble phosphates, water soluble phosphates whenmixed with superabsorbent polymers and fertilizers demonstrated improvedabsorbance.

The invention claimed is:
 1. A composition comprising: (i) at least onesuperabsorbent polymer, and (ii) at least one water soluble phosphate inan amount of 0.1% to 25% of the total weight of the at least onesuperabsorbent polymer, wherein the at least one water soluble phosphateis selected from the group consisting of monosodium phosphate, disodiumphosphate, trisodium phosphate, rock phosphate, monopotassium phosphate,potassium diphosphate, and dipotassium phosphate.
 2. The compositionaccording to claim 1, wherein the composition further comprises at leastone plant advantageous additive.
 3. The composition according to claim1, wherein the superabsorbent polymer is selected from the groupconsisting of copolymer of acrylamide and sodium acrylate; hydrolyzedstarch-polyacrylonitrile; 2-propenenitrile homopolymer, hydrolyzed,sodium salt or poly(acrylamide co-sodium acrylate) orpoly(2-propenamide-co-2-propanoic acid, sodium salt);starch-g-poly(2propenamide-co-2-propanoic acid, mixed sodium andaluminum salts); starch-g-poly(2-propenamide-co-2-propanoic acid,potassium salt); poly(2-propenamide-co-2-propanoic acid, sodium salt);poly-2-propanoic acid, sodium salt; starch-gpoly(acrylonitrile) orpoly(2-propenamide-co-sodium acrylate); starch/acrylonitrite copolymer;crosslinked copolymers of acrylamide and sodium acrylate;acrylamide/sodium polyacrylate crosslinked polymers; anionicpolyacrylamide; starch grafted sodium polyacrylates; acrylic acidpolymers, sodium salt; crosslinked potassium polyacrylate/polyacrylamidecopolymers; sodium polyacrylate; superabsorbent polymer laminates andcomposites; partial sodium salt of crosslinked polypropenoic acid;potassium polyacrylate, lightly crosslinked; sodium polyacrylate,lightly crosslinked; sodium polyacrylates; poly(sodiumacrylate)homopolymer; polyacrylamide polymers, carrageenan, agar, alginic acid,guar gums and its derivatives, and gellan gum; crosslinked copolymer ofacrylamide and potassium acrylate.
 4. The composition according to claim1, wherein said superabsorbent polymer is starch-g-poly(2-propenamide-co-2-propenoic acid) potassium salt or crosslinkedpolyacrylic acid potassium salt.
 5. The composition according to claim1, wherein the water soluble phosphate is trisodium phosphate.
 6. Thecomposition as claimed in claim 2, wherein the plant advantageousadditive is selected from fertilizers, mycorrhiza, micronutrients,acaricides, algicides, antifeedants, avicides, bactericides, birdrepellents, chemosterilants, fungicides, herbicide safeners, herbicides,insect attractants, insect repellents, insecticides, mammal repellents,mating disruptors, molluscicides, nematicides, plant activators,plant-growth regulators, rodenticides, synergists, virucides,derivatives thereof, biological control agents and mixtures thereof. 7.The composition as claimed in claim 2, wherein the plant advantageousadditive is a fertilizer selected from urea, NPK, nitrogen basedfertilizers, phosphate, calcium, potassium, magnesium, sulfur, copper,iron, manganese, molybdenum, zinc, nickel, cobalt, boron and their saltsand derivatives, peat, limestone, rock phosphate, Blood meal, bone meal,compost, humic acid, amino acids, seaweed extracts, digested proteins,fish meal, feather meal, potassium carbonate, potassium chloride,potassium sulfate, potassium nitrate, sulfate of potash magnesia; zincsulfate, zinc oxide, zinc ammonia complex; Di-ammonium phosphate,Monoammonium phosphate, Ammonium polyphosphate, Triple superphosphate ormixtures thereof.
 8. The composition according to claim 1, furthercomprising at least one pesticide.
 9. A method of increasing waterabsorption capacity of a superabsorbent polymer, the method comprisingcontacting the superabsorbent polymer with at least one water solublephosphate in an amount of 0.1% to 25% of the total weight of the atleast one superabsorbent polymer; wherein the at least one water solublephosphate is selected from the group consisting of monosodium phosphate,disodium phosphate, trisodium phosphate, rock phosphate, monopotassiumphosphate, potassium diphosphate, and dipotassium phosphate.
 10. Themethod according to claim 9, wherein said superabsorbent polymer isstarch-g-poly (2-propenamide-co-2-propenoic acid) potassium salt orcrosslinked polyacrylic acid potassium salt and said water solublephosphate is trisodium phosphate.
 11. The composition according to claim1, wherein the at least one water soluble phosphate is in an amount of0.1% to 20% of the total weight of the at least one superabsorbentpolymer.
 12. The composition according to claim 1, wherein the at leastone water soluble phosphate is in an amount of 0.1% to 10% of the totalweight of the at least one superabsorbent polymer.